Show some panels if XDG_CURRENT_DESKTOP is not set
Some people (yup, really!) still run gnome-control-center through sudo, which means that XDG_CURRENT_DESKTOP is not set. In that case, all panels are missing, which is pretty stupid.
We should show at least certain panels that are more universally useful rather than presenting the user with an emtpy shell.
Candidates are:
- Users
- Time and Date
- Any network settings
Not shown should probably be:
- Displays (requires mutter to be useful)